Uses the "Largest Remainder Method" to ensure rounded percentages add up to their correct total

Readme.md

PercentRounder

Uses the Largest Remainder Method to ensure rounded percentages add up to their correct total while preserving their order.

💪

Examples:

PercentRounder.Compute(13.626332, 47.989636, 9.596008, 28.788024);
// result: 14, 48, 9, 29

Related:

• https://en.wikipedia.org/wiki/Largest_remainder_method
• https://stackoverflow.com/questions/13483430/how-to-make-rounded-percentages-add-up-to-100

PercentRounder.cs

using System;
using System.Collections.Generic;
using System.Linq;

public class PercentRounder
{
    public class PercentInfo
    {
        public int Index;
        public int Percent;
        public decimal Remainder;

        public PercentInfo(int index, decimal number)
        {
            Index = index;
            Percent = (int)Math.Floor(number);
            Remainder = (int)(((decimal)number % 1) * 100);
        }
    }

    public static List<int> Compute(params decimal[] numbers)
    {
        var total = (int)Math.Round(numbers.Sum());
        var values = numbers
            .Select((p, index) => new PercentInfo(index, p))
            .OrderByDescending(p => p.Remainder).ToList();
        var remainder = total - values.Sum(p => p.Percent);

        foreach (var value in values)
        {
            if (remainder == 0) break;

            value.Percent++;
            remainder--;
        }

        return values.OrderBy(p => p.Index).Select(p => p.Percent).ToList();
    }
}